Mice lacking the p75(NGFR) receptor exhibit abnormal responses to light

A role for nerve growth factor (NGF) in the mammalian circadian system was assessed in mice using a line of gene targeted animals carrying a null mutation at the low affinity p75(NGFR) receptor locus. Receptor-deficient mice exhibited positive phase angles of entrainment to 24 h light-dark cycles. In constant dark, circadian rhythms of behavior were normal but phase shifts induced by brief pulses of light were significantly decreased. These results support the hypothesis that NGF, through an action mediated at least in part by p75(NGFR) receptors in the SCN, is involved in the regulation of circadian responses to light.